#331

Verify Preorder Serialization of a Binary Tree

specialist · 910 · lc medium +31 · verified · 47.1% accepted · 2,453 likes · top 32%

Description

One way to serialize a binary tree uses preorder traversal, recording node values and using a sentinel value such as '#' for null nodes.

Given a comma-separated string preorder, return true if it is a valid preorder serialization of some binary tree, or false otherwise.

Each token is either an integer or '#'. You are not allowed to reconstruct the tree.

Example 1:

Input: preorder = "9,3,4,#,#,1,#,#,2,#,6,#,#"

Output: true

Example 2:

Input: preorder = "1,#"

Output: false

Example 3:

Input: preorder = "9,#,#,1"

Output: false

Code

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class Solution:
    def isValidSerialization(self, preorder: str) -> bool:

class Solution:
    def isValidSerialization(self, preorder: str) -> bool: